23.3.5 Procedure in the SGSN
29.0023GPPMobile Application Part (MAP) specificationRelease 17TS
Any CAMEL-specific handling defined in this clause is omitted if the SGSN does not support CAMEL control of MT SMS, or if the subscriber does not have a subscription for CAMEL control of MT SMS.
The process starts when the SGSN receives a dialogue opening request with the application context shortMsgMT-RelayContext. The MAP process invokes macros not defined in this clause; the definitions of these macros can be found as follows:
Receive_Open_Ind see clause 25.1.1;
Check_Indication see clause 25.2.1.
The mobile terminated short message transfer process in the SGSN is shown in figure 23.3/10.
Procedure MT_SM_SGSN sheet 1: The decision box "TCAP Handshake required" takes the "yes" or "no" exit depending on agreements between the Serving SGSN’s operator and the SMS Gateway MSC’s operator (see 3GPP TS 33.204 [34a]).
The macro MT_SM_Transfer_SGSN is used to transfer the first MT short message of a possible sequence of messages. It is shown in figure 23.3/11.
If the MS is using extended idle mode DRX (as defined in 3GPP TS 23.682 [148]) and the MS is expected to respond to paging shortly or within the time frame indicated by the SM-Delivery-Timer and SM-Delivery-Start-Time IEs, the SGSN should page the MS and attempt to deliver the short message to the MS.
If the MS is using extended idle mode DRX (as defined in 3GPP TS 23.682 [148]) and the MS is expected to not respond to paging shortly or within the time frame indicated by the SM-Delivery-Timer and SM-Delivery-Start-Time IEs, the SGSN may behave as specified in figure 23.3/11 for an MS that is not reachachable, i.e. set the MNRG flag and return an Absent Subscriber Error to the SMS-GMSC, while still paging the MS.
NOTE 1: This mechanism is not intended for MSs which are known to wake up shortly (e.g. within the next 10 seconds) as enough time needs to elapse, between the sending of the MT Forward Short Message Response and the subsequent Ready For SM procedure towards the HLR when the MS becomes reachable, for the Report SM Delivery Status procedure to take place beforehand from the SMS-GMSC to the HLR.
If the MS is using a power saving mechanism such as extended idle mode DRX (see 3GPP TS 23.682 [148]), and if the MT Forward Short Message Request includes the Maximum Retransmission Time IE, the SGSN may return an MT Forward Short Message Response with the User Error set to Absent Subscriber_SM and with the Requested-Retransmission-Time IE requesting the SMS-GMSC to retransmit the Short Message at a later time prior to the Maximum Retransmission Time. In that case, the SGSN shall store (if not already done) the SMS-GMSC address and, if available, the SMS-GMSC Diameter Identity received in the request and shall not set the MNRG flag.
NOTE 2: This mechanism does not cause additional signalling at the HSS to retransmit the Short Message.
The SGSN shall initiate the MAP Service Center Alert procedure to alert the SMS-GMSC when the UE, for which one or more MT SMS have been requested to be retransmitted at a later time, becomes available for MT SMS delivery or moves under the coverage of another MME or SGSN prior to the requested SM retransmission time. The SGSN shall then delete the stored SMS-GMSC address after the Alert Service Centre procedure is completed.
The macro Check_Subscr_Identity_For_MT_SMS is shown in figure 23.3/8. The page and search procedures are shown in figures 23.3/12 and 23.3/13.